Hydraulic rotary piston machine

ABSTRACT

The invention relates to a rotary piston machine of the type having an externally toothed star member and a surrounding internally toothed ring member. The star and ring members have cooperably engaging teeth and are eccentrically offset relative to each other. The ring member teeth are in the form of rotatable rollers which are journaled in casing portions on opposite sides of the ring member. The ring member has slots in radially aligned and surrounding relation to the rollers and plates in the slots are biased into sealing engagement with the rollers by spring means and/or hydraulic means.

United States Patent inventor Carl V. Olu'berg Havnbjerg, Denmark Appl.No. 46,280 Filed June 15, 1970 Patented Get. 19, 1971 Assignee DanfossA/S Nordborg, Denmark Priority June 19, 1969 Germany P 19 31 143.4

HYDRAULIC ROTARY PISTON MACHINE Primary Examiner-Carlton R. CroyleAssistant Examiner-John J. Vrablik Attorney-Wayne B. Easton ABSTRACT:The invention relates to a. rotary piston machine of the type having anexternally toothed star member and a surrounding internally toothed ringmember. The star and ring members have cooperably engaging teeth and areeccentrically offset relative to each other. The ring member teeth arein the form of rotatable rollers which are journaled in casing portionson opposite sides of the ring member. The ring member has slots inradially aligned and surrounding relation to the rollers and plates inthe slots are biased into sealing engagement with the rollers by springmeans and/or hydraulic means.

PATENTEUHCI 1s |97| sum 1 0F 2 31514 2 74 HYDRAULIC ROTARY PISTONMACHINE The invention relates to a hydraulic rotary piston machine, inwhich an externally toothed wheel cooperates with an internally toothedring, the teeth of which are constituted by rollers which are arrangedin recesses in an outer ring and are mounted in side portions connectedto this outer ring.

In rotary piston machines of this kind, which may operate as pumps ormotors, the axes of the toothed wheel and the toothed ring are offsetfrom each other; it is also possible for the center point of one toothedelement to revolve about the center point of the other toothed element.During this movement the teeth of the toothed wheel are in close contactwith and slide over those of the outer ring, and between the teeth andthe side portions there are formed displacement chambers which increaseand decrease in size cyclically.

By forming the teeth of the toothed ring as rollers, manufacture can besimplified. Furthermore, these rollers should rotate during the slidingcontact with the teeth of the toothed wheel, so that wear is reduced. Inthis connection however difficulties are encountered in practice.

In a first known arrangement, short rollers, the length of whichcorresponds to the width of the outer ring, are mounted in the recessesthemselves. Here a compromise must be made. On the one hand, the rollersmust fit the recesses so well that no path is created along which thefluid under pressure can leak; on the other hand however there must be asufficient clearance to allow the rollers to be properly lubricated.This system is particularly sensitive to dirt which can force its waybetween the rollers and the recesses. Furthermore, the loosely fittedrollers are not only loaded on one side by the toothed ring but also bythe hydraulic fluid, so that increased mechanical friction between therollers and certain points in the recesses results.

The last-mentioned disadvantage is avoided in a construction in whichcylindrical rollers of greater length are used and these are mounted inboth side portions. The other disadvantages are however still present.Furthermore, in practice it is virtually impossible for three parts,namely the two side plates and the outer ring containing the recesses,to be so produced, aligned and kept in alignment during the period ofoperation, in such a manner that no jamming of the rollers occurs.

The object of the invention is to provide a hydraulic rotarypistonmachine of the initially described kind in which the rollers can rotatefreely with little friction and in which, at worst, insignificant lossesof oil due to leakage occur.

According to the invention this object is achieved by arranging therollers in the recesses so that there is clearance between them and bycausing a sealing slide pin, guided in the outer ring, to be pressedagainst the periphery of each roller.

In this construction it is only necessary for the spaced-apart bearingsfor each roller to be aligned with each other in the two side portions.This problem can be readily solved. Since there should be clearancebetween the roller and the recess, there is very considerable latitudefor the alignment of this recess with the bearings. Furthermore, theclearance allows the compressed fluid to penetrate behind the rollersand thus to relieve them of load. The sealing slide pins prevent lossesdue to leakage, despite this clearance. Dirt causes no trouble at all inthe gap and, if it passes over the top of the roller and below thesealing slide pin, it merely leads to the pin being lifted from theroller for a brief period. Thus, perfect low-friction operation isensured.

Each sealing slide pin can be spring loaded. Instead of or in additionto this, each sealing slide pin can also be loaded by the pressure ofthe hydraulic medium. The latter has the advantage that in the case ofhigher working pressures, which tend to causelosses by leakage, a highersealing pressure is also applied by the slide pins.

In particular, the lower ends of all the grooves in which the sealingslide pins are guided can be connected to a common passage system whichis connected to the pressure side of the machine. In the case of areversible rotary-piston machine it is advisable to connect the commonpassage system of passages to the two unions by way of a nonretum valvein each case. Then automatically caters for the passage system alwayscontaining hydraulic medium at higher pressure.

The rollers can be held in the side portions in bearings, either plainbearings or roller hearings, in order to reduce friction still further.The invention will now be described in more detail by reference to anembodiment illustrated in the drawing, in which:

FIG. 1 is a longitudinal section through a rotary piston machineconstructed in accordance with the invention, and

FIG. 2 shows a section on line A-A of FIG. 1.

The casing of the rotary piston machine illustrated consists of abearing portion 1, an intermediate part 2, a side portion 3, an outerring 4, a second side portion 5, a slide plate 6, a casing ring 7 and acover plate 8. The parts 1-5 are interconnected by screw bolts 9, andthe parts 4-8 by screwbolts 10.- A main shaft 11 is mounted in bearings12 and 13 in the bearing portion 1. A universal-joint shaft 14 which,through an outer toothed portion at both ends engages in a correspondinginner toothed portion, connects the main shaft 17 to an internallytoothed ring 15. This toothed ring meshes with rollers 16, which arerotatably mounted in bearings 17 and 18 in the side portions 3 and 5 andare fitted in recesses 19 in the outer ring 4, there being clearancebetween the nollers and the recesses. Between the teeth of the toothedring 15, the roller 16, the rest of the outer ring 4 and the two sideportions 3 and 5 there are thus formed displacement chambers 20, whichincrease and diminish in size cyclically with each revolution of thetoothed wheel 15.

Sealing slide pins 21 are guided in grooves 22 in the outer ring 4 andare pressed against the peripheral surfaces of the rolls 16 by a leafspring 23 or the pressure obtaining in the chamber 24. This results in aperfect seal between adjacent displacement chambers 20, despite theclearance between each roller 16 and recess 19.

The sealing slide pins 21 are intended only to effect a seal andtherefore do not need to reciprocate as in slide valve pumps orpusher-type engines. The accuracy of the machining of the grooves andsurfaces of the slide pins does not therefore need to be as great.Furthermore, the rate of revolution of the rollers is very low; noparticularly heavy demands are therefore made on the material cf theslide pins and a casehardened steel is adequate.

The spaces 24 below the pusher pins 21 are interconnected through anannular groove 25 in the side potion 5. This annular groovecommunicates, by way of axial passages 26, with an annular groove 27which in turn communicates through two similar paths with the unions 28and 29 in the cover plate 8. Only one of these paths is shown. itconsists of an axial bore 30 in the slide plate 6, a nonretum valve 31in the casing ring 7 and a connecting passage 32 in the cover plate 8.The nonretum valve ensures that the spaces 24 in each case communicatewith the side under higher pressure, even when the machine is of thekind that can operate in reverse.

An astial passage 33 in the side portion 5 leads into the displacementchambers 20 between each two rollers 16, and this passage is continuedas an axial passage 34 in the slide part 6. Since nine rollers 16 arepresent in this embodiment, there are also nine such passages 33, 34.Cooperating with the mouths of the passages 34 is a rotary slide valve35, which is driven at the same speed as the toothed ring 15 by auniversal-joint shaft 36, both ends of which likewise engage through anouter toothed portion with corresponding inner toothed portions. Therotary slide valve 35 is mounted on the journal 37 which is held in thecover plate 8. The rotary slide valve contains eight openings 36 whichcommunicate with; the unions 28 through an annular groove 36, andbetween each pair of these openings the rotary slide valve containseight further openings 40 which communicate with the union 29 through anannular groove 41. In this way the rotary slide valve 35 and the slideplate 6 constitute a commutator valve: which ensures that thedisplacement chambers 20 are connected in the correct sequence with thehigh-pressure and low-pressure sides of the machine respectively.

To relieve the rotary slide valve of pressure, the openings 38 areinterconnected on that side opposite the annular sleeve 39 by an annulargroove 42, and the openings 40 are interconnected on that side oppositethe annular groove 41 by an an nular groove 43. Moreover, a recessedarea 44, similar to the mouth, is provided in the cover plate 8 oppositeeach of the passages 34, and from each opening 38, 40 there runsa-cutoff passage 45 which extends to the end face of the cover plate 8,so that the same pressure obtains in the recesses 44 as at the mouths ofthe passages 34.

All spaces into which leaking oil can penetrate, and particularly thecentral spaces 46, the space 47 for the bearing and the space 48 outsidethe rotary slide valve are interconnected through passages 49, 50 and51. Fitted in the cover plate 8 are two nonreturn valves (notillustrated) through each of which the leaking oil is passed to thelow-pressure union.

The embodiment described relates to a specific type of rotary pistonmachine. The principle of forming the teeth as rollers, here described,can however also be used in any other geared or rotary piston machines.

I claim:

I. A rotary piston machine comprising an externally toothed wheel memberand a surrounding internally toothed ring member, said members havingcooperably engaging teeth and being eccentrically offset relative toeach other, a casing.

including casing portions on opposite sides of said ring member, saidring member having teeth formed as cylindrically shaped rollers, saidrollers being joumaled in said casing portions, said ring memberdefining slots in radially aligned and surrounding relation to saidrollers, plates in said slots, and biasing means biasing said platesinto sealing engagement with said rollers.

2. A rotary piston machine according to claim 1 wherein said ring memberhas circumferentially arranged recesses, said rollers being disposed insaid recesses.

3. A rotary piston machine according to claim 1 wherein said biasingmeans are springs.

4. A rotary piston machine according to claim 1 wherein said biasingmeans includes channel means having fluid communication with the outerends of said slots, and means for supplying pressurized fluid to saidchannel means.

5. A rotary piston machine according to claim 4 wherein said casingincludes inlet and outlet ports, said channel means having fluidcommunication with said inlet port.

6. A rotary piston machine according to claim 5 wherein said channelmeans has fluid communication with said outlet port, and one way valvemeans disposed between said ports and said channel means.

1. A rotary piston machine comprising an externally toothed wheel memberand a surrounding internally toothed ring member, said members havingcooperably engaging teeth and being eccentrically offset relative toeach other, a casing including casing portions on opposite sides of saidring member, said ring member having teeth formed as cylindricallyshaped rollers, said rollers being journaled in said casing portions,said ring member defining slots in radially aligned and surroundingrelation to said rollers, plates in said slots, and biasing meansbiasing said plates into sealing engagement with said rollers.
 2. Arotary piston machine according to claim 1 wherein said ring member hascircumferentially arranged recesses, said rollers being disposed in saidrecesses.
 3. A rotary piston machine according to claim 1 wherein saidbiasing means are springs.
 4. A rotary piston machine according to claim1 wherein said biasing means includes channeL means having fluidcommunication with the outer ends of said slots, and means for supplyingpressurized fluid to said channel means.
 5. A rotary piston machineaccording to claim 4 wherein said casing includes inlet and outletports, said channel means having fluid communication with said inletport.
 6. A rotary piston machine according to claim 5 wherein saidchannel means has fluid communication with said outlet port, and one wayvalve means disposed between said ports and said channel means.